Allow PPTP VPN connection on firewalld

To allow PPTP VPN connection when using firewalls, run the following commands.

Allow 1723/tcp

sudo firewall-cmd --permanent --zone=public --add-port=1723/tcp

Allow gre protocol

firewall-cmd --permanent --add-rich-rule='rule protocol value="gre" accept'

or

sudo firewall-cmd --permanent --zone=public --direct --add-rule ipv4 filter INPUT 0 -p gre -j ACCEPT
sudo firewall-cmd --permanent --zone=public --direct --add-rule ipv6 filter INPUT 0 -p gre -j ACCEPT

Enable IP masquerade

sudo firewall-cmd --permanent --zone=public --add-masquerade

Reload firewall.

sudo firewall-cmd --reload

See firewalld